Okay so I made a new world and I started building a house and making the land flat. I then decided to leave my new world to go back to my old world to collect stuff to bring over and I did not have enough inventory room so I dropped/threw a whole bunch of my stuff on the ground (I did not place it like you are supposed to). Anyways when I left my new world and got my stuff from my old world I returned and where I dropped/threw all my stuff was now an empty shallow hole in the ground in the middle of my house.
Now every time I patch it up and exit the game and go to play again later the hole is back and my patchwork has disappeared. What went wrong? I really don't want to tear down my house that I have already built so much of.